With traditional analog techniques, the challenge of choosing colors for graphical elements such as company logos consisted solely in making the right color choice from among the colors in a specially printed swatch book. A graphic designer could focus on choosing a color that embodies the image the client wanted to project and once the choice was made, it could be simply and reliably communicated to a print service provider. In the case of the swatch books most popular in North America and Europe—the PANTONE® Formula Guide—the graphic designer simply specifies the name of the Pantone color (e.g. “PANTONE 653 C”—i.e., HP's corporate identity color) and a physical color chip showing the actual color could also be provided for additional reassurance. The print service provider would then look up the chosen color and from there translate the named color into a combination of the basic inks required to reproduce the specified Pantone color. Hence not having a good idea on how close that ink combination would result from the intended Pantone reference.
Today, however, the neat and simple approach described above is not accurate enough due to the ever increasing use of a variety of digital printing systems, which are not compatible with the use of the fifteen basic Pantone inks, but, instead, rely on their own specific printing techniques which might, e.g., be based on a different set of inks and ways of addressing their use. Even more all selection criteria are hidden from the designer which is just confronted to a choice that has been made to him/her without a real control of the possibilities that were available. With each printing system, a different range of printable colors (i.e. color gamut) is obtained, and, furthermore, the range of obtained colors also depends on the particular print medium used in combination with the digital printing system. In general, the obtained range of colors does not include all of the reference colors, making it necessary to try to reproduce as much as possible a predetermined color choice in a given printing system, resulting in trial and error sessions with preparation stages for example in a pre-press process without guarantee of satisfactory final results.
As a result, the task of the graphic designer becomes significantly more complex in cases where a design is to be printed, even if at least partially, digitally. If, for example, a company wishes to print a large format poster that includes their logo (whose color is defined in Pantone terms) or if a number of leaflets or brochures is to be printed using a laser printer or digital press, then the designer needs to deal with the gamut differences between the Pantone set and the digital printing systems—which are usually not yet known at design phase.
This problem is addressed by reference color simulation techniques which aim at finding for each reference color its best representation in the gamut of a particular combination of printer and print medium.
Providing good simulations of Pantone colors on a given medium is clearly very important, but color simulation techniques are purely computational approaches which often do not address the problem of usability and interactivity of digital color simulation systems, specially taking into account the large variety of possibilities that a user has, e.g., changing inks, media, or printing devices.
The proposed invention thus addresses aspects which are related to the usability of a color simulation system, e.g. the following problems: First, when looking at a digital print it can be a challenge to see how well a Pantone color is simulated with just the original PANTONE Formula Guide available as what one compares is a relatively small color chip, on the one hand, and a colored graphical element, like a logo, on the other. Second, when looking at a simulation which looks different from the pre-determined Pantone color, it is not clear whether the differences are genuinely due to an inherent gamut difference between printed or emitting media or due to workflow issues. Third, before printing Pantone simulations on a digital printing system the designer does not know how close the simulation will be to the pre-determined color. Fourth, if matching a Pantone color is more important than the choice of media used in the digital printing system the designer is currently faced with many trial and error sessions. Fifth, if the agreement between pre-determined and digitally simulated colors is more important than the precise color choice, again the designer needs to do significant trial and error work.
In order to reduce trial and error work, it is known to work in a simulated color space which represents both a specific cluster associated to a specific color representation system used by the designer and the pre-determined color. The cluster is typically formed by the colors which may be obtained with the specific color representation system. The pre-determined color is the color which the designer wishes to reproduce. The designer may then pick in the color space the color point being part of the cluster which is closest to (or, in an ideal case, which is the same as) the original color.